Method and device for producing a flame, particulary for coloured flame lamps

ABSTRACT

Method for producing a flame, particularly for coloured flame lamps using a small liquid flow at the upper end of a rising tube ( 4 ) of small transverse cross-section, the method consisting in allowing combustible gas in the form of a sequence of bubbles to pass into a bubble chamber ( 3 ) placed at the lower end of the rising tube, the gas bubbles ( 13, 17 ) having a cross-section at least equal to the transverse cross-section of the rising tube and in igniting and letting the mixture of combustible gas and liquid burn at said upper end of the rising tube. The liquid may contain a chemical compound chosen for the colour it can impart to the flames.

The present invention relates to a straightforward and inexpensive method and device for producing a flame, particularly for coloured flame lamps. The invention implements a known steady low feed rate system wherein a liquid is made to rise, by means of a string of bubbles, into a tube of small cross-section. Such a system is described particularly in documents U.S. Pat. No. 5,312,232, 4,645,427 and 4,647,272.

Lighters and flame lamps using gas and particularly liquefied gas combustion are known and in widespread use.

It is known furthermore that it is possible to colour flames by injecting into them chemical compounds having the property of colouring them. This injection is, however, tricky to implement when it is required to make a flame lamp of simple design, fed by gas and particularly liquefied gas, at a low and steady rate of flow, without running the risk of blocking the gas and chemical compound feed means.

The objective for the invention is to eliminate the drawbacks of prior art solutions by introducing a method and a device for producing a flame particularly a coloured flame which are characterised by great simplicity and low cost. The technology implemented by the present invention consists in raising a liquid in a tube of small cross-section from a lower level to a higher level, without applying pressure to this liquid, or by applying to the liquid a pressure lower than that normally required to raise it by the same height, the liquid rising under the action of bubbles of a combustible gas. In this way the technical problem mentioned above is resolved by means of the invention.

The invention relates firstly to a method for producing a flame by combustion of a combustible gas at the upper end of a rising tube of small internal transverse cross-section, characterised in that:

a) a supply of a liquid is set up with its level being maintained both below that of the upper end of said rising tube and above that of the lower end of this same tube,

b) the supply of liquid is brought into contact with a chamber, called a bubble chamber, that also communicates with the lower end of said rising tube, or is inserted into the latter in its lower part and also communicating with a combustible gas source by means of a gas inlet port,

c) while maintaining the liquid level of the supply as shown above, the combustible gas is allowed to pass into the bubble chamber through the gas inlet port at a sufficient rate of flow to produce at the base of the rising tube a sequence of combustible gas bubbles in the liquid, said rate of flow being however smaller than that which would lead to an accumulation of gas below the rising tube such that the liquid would no longer have access to the lower end of this tube, and said sequence of combustible gas bubbles separated by portions of entrained liquid is allowed to rise in the rising tube, and

d) the mixture of combustible gas bubbles and liquid is ignited and allowed to burn, at said upper end of the rising tube, so as to operate as a flame lamp.

The invention also relates to a device including a rising tube communicating via its lower end with a chamber called a bubble chamber, said bubble chamber being furthermore in communication on the one hand with a tank for liquid and on the other hand with a combustible gas source, said tank being able to contain said liquid at a level both above the level of the lower end of the rising tube and below the level of the upper end of said rising tube, the bubble chamber and the combustible gas source communicating by means of a gas inlet port, said device being characterised in that it additionally comprises a burner at the upper end of the rising tube, intended for the combustion of the combustible gas and any liquid, as well as means for controlling the rate of flow of the combustible gas allowing the latter to pass into the liquid in the form of a string of successive gas bubbles with a cross-section at least equal to the internal cross-section of the rising tube, directed towards the base of the rising tube or introduced directly into it.

It will be easily understood that the bubbles of combustible gas may distort as they penetrate into the rising tube and that they are able to take on a different shape, particularly elongated in the direction of their rise. They remain however separated from each other while entraining portions of liquid between them.

It will also be understood that the transverse cross-section of the rising tube depends on the size of the bubbles created since each bubble, in said tube, must be in contact with the walls and must therefore be able to occupy the full cross-section of the tube.

Several forms of implementation and manufacture are conceivable.

In a first form of implementation of the method of the invention, the latter consists of a method for producing a flame by combustion of a combustible gas at the upper end of a rising tube of small internal transverse cross-section characterised in that:

a) a supply of a liquid is set up with its level being maintained both below that of the upper end of said rising tube and above that of the lower end of this same tube,

b) the supply of liquid is brought into contact with a chamber, called a bubble chamber, that also communicates on the one hand, at its upper part, with the lower end of said rising tube and on the other hand with a combustible gas source by means of a gas inlet port which is located at a level of the bubble chamber below the level of the lower end of the rising tube, the cross-section of the gas inlet port in the bubble chamber being sufficient so as to produce in the bubble chamber liquid successive gas bubbles with a cross-section at least equal to the internal transverse cross-section of the rising tube, the liquid in the supply being brought into contact with the bubble chamber away from the path of said gas bubbles,

c) while maintaining the liquid level in the supply as shown above, the combustible gas is allowed to pass into the bubble chamber through the gas inlet port at a sufficient rate of flow to produce a sequence of combustible gas bubbles in the liquid, said rate of flow being smaller however than that which would lead to an accumulation of gas bubbles at the top of the bubble chamber, so as to allow said sequence of combustible gas bubbles separated by portions of entrained liquid to rise in the rising tube and to release said portions of liquid at the upper end of said rising tube, and

d) the mixture of combustible gas bubbles and liquid is ignited and allowed to burn, at said upper end of the rising tube, so as to operate as a flame lamp.

In a first embodiment of the device of the invention, the latter consists of a device including a rising tube communicating via its lower end with the upper end of a chamber called a bubble chamber, said bubble chamber being furthermore in contact on the one hand with a tank for liquid and on the other hand with a combustible gas source, said tank being able to contain said liquid at a level both above the level of the lower end of the rising tube and below the level of the upper end of said rising tube, the bubble chamber and the combustible gas source being brought into contact by means of a gas inlet port located at a level of the bubble chamber below the level where said chamber communicates with the lower end of the rising tube and the bubble chamber and the liquid tank being brought into contact by means of at least one liquid inlet port located away from the rising path followed by the combustible gas bubbles which are able to form when the bubble chamber is filled with liquid and when the gas is allowed to pass into said chamber, said device being characterised in that it additionally comprises a burner at the upper end of the rising tube, intended for the combustion of the combustible gas and any liquid, as well as means for controlling the rate of flow of the combustible gas allowing the latter to pass into the bubble chamber in the form of a string of successive gas bubbles with a cross-section at least equal to the internal transverse cross-section of the rising tube.

According to a preferred form of implementing the first embodiment of the invention, the transverse cross-section of the bubble chamber is larger than both the maximum internal transverse cross-section of the rising tube and the transverse cross-section of the gas inlet port in the bubble chamber.

In a second form of implementing the invention, the level of the lower end of the rising tube is lower than the top of the bubble chamber and the gas is allowed to pass under sufficient pressure to push back the liquid from its rest level, downwards, as far as the vicinity of the level of the lower end of the rising tube, thus allowing the gas to access this lower end of the rising tube in the form of a string of successive bubbles.

In this second embodiment, a space may be provided surrounding the rising tube, or in its vicinity, and thereby extending the bubble chamber upwards, and this space must be made impermeable so as to allow the gas to exert its delivery pressure on the liquid surrounding, at rest, the rising tube, or in its vicinity. The gas pressure must be limited to that which allows the liquid to drop to the level of the lower end of the rising tube or to its vicinity. Indeed, excessive pressure would push the liquid back to a level such that this liquid would no longer access the rising tube. This pressure is therefore low and equal to the head of liquid to bring down.

In this second embodiment, the pressurised gas may be allowed to pass into a space surrounding the rising tube, or in its vicinity, and at a level above the level of the lower end of this tube. The gas may also be allowed to pass directly into the liquid. It then forms bubbles, which, as they release their gas into the sealed space surrounding the rising tube, or in its vicinity, allow the liquid to be pushed back to the level of the lower end of the rising tube, as in the previous case.

In a third embodiment, the gas is allowed to pass directly inside the rising tube, at its lower part, at a level below the level reached by the liquid at rest, in the absence of gas injection. This lower part then acts as the bubble chamber. In this case however the gas port must not occupy the entire cross-section of the tube, so as to leave room to pass for the liquid that is to rise in the tube. It must however be of sufficient size for the formed bubbles, which, as a general rule, are of larger diameter than the gas port, as will be explained below, to have a sufficient size to occupy the entire transverse cross-section of the rising tube.

Whichever embodiment is selected, the flows of liquid and combustible gas are proportioned in the bubble chamber located at the base of the rising tube and fitted with three ports as follows:

-   -   a gas feed port the cross-section of which determines the size         of the bubbles formed,     -   an inlet port allowing the liquid to pass in from its tank. The         geometry of this second port is not critical, so long as it is         located at a point of the chamber such that the bubbles of gas         formed are not able to penetrate into it instead of penetrating         into the rising tube. This risk may be further reduced by         shrinking the size of this second port or by positioning it at a         level below the level of the gas inlet into the bubble chamber.     -   a port for the outflow of the string of bubbles at the upper end         of the bubble chamber, said port consisting of the low end of         the rising tube. In the first embodiment of the invention, this         port is preferably placed above the gas feed nozzle and it is to         advantage preceded by an upturned funnel access to facilitate         bubble collection and to prevent them from dividing.

The rate of flow of the combustible gas is preferably substantially larger than the rate of flow of liquid feed on a volumetric basis, for example 5 to 20 times larger.

It is considered that in the first embodiment of the invention, the gas bubbles in the feed liquid by forming bubbles with a (horizontal) transverse cross-section at least equal to and preferably larger than the maximum internal cross-section of the rising tube. This is obtained by adjusting the gas inlet port. This port may have a cross-section that is slightly smaller than that of the rising tube since the bubbles tend to increase in cross-section and in volume as they leave the gas inlet port. The cross-section of this port may, to advantage, be 25 to 100% of the maximum internal cross-section of the rising tube, provided it respects the size condition of the formed bubbles. This size of the formed bubbles depends to a certain extent on the nature of the liquid, on its density and on its viscosity. Increasing the viscosity of the liquid generally tends to lead to the formation of larger bubbles at the outlet of the gas inlet nozzle.

The idea of “maximum internal cross-section” of the rising tube refers to the situation of a tube with an internal cross-section that is not constant at all levels. In the more common case of a tube of constant internal cross-section, the maximum internal cross-section is equal to the (constant) internal cross-section of the tube.

The rate of flow of the combustible carrier gas is selected as a function of the rate of flow required for the rising liquid feed. It is however limited as a function of the assembly and particularly of the cross-section and of the length of the rising tube. Thus, in this tube, each gas bubble is separated from the previous one and from the next one by a small quantity of liquid that finds itself entrained upwards in the tube. An excessive rate of flow of gas could lead to an accumulation of gas in the upper part of the bubble chamber and the liquid would then no longer be entrained into the rising tube.

As the level of the top of the rising tube is located above the load level of the liquid in the feed tank, the liquid is entrained higher than this level of the tank by the effect of the string of gas bubbles. As a consequence, stopping the gas feed causes the liquid outflow to stop.

According to a preferred embodiment of the invention, the transverse cross-section of the rising tube is, at all points, less than 1 square centimetre, and preferably less than 10 square millimetres, so as to ensure that the liquid pushed upwards by the string of bubbles slides as little as possible between these bubbles and the wall of the rising tube. To obtain a rate of flow of liquid that is even smaller, said cross-section may be from 1 to 5 square millimetres.

According to another embodiment, the source of gas bubbles in the bubble chamber consists of a single aperture, thus creating a single column of successive gas bubbles in the liquid.

The burner, provided at the upper end of the rising tube, may consist simply of the upper end of the rising tube. This can also be a porous body that is non-combustible or difficult to combust, able to be impregnated with the liquid that has gathered at the top of the rising tube. The porous body may for example be made of a sintered metal, porous porcelain, porous concrete, sintered porcelain or else consist of a wick similar to that in an oil lamp.

The burner may also comprise a piece of metal gauze, a wire yarn sleeve, that may or may not be meshed, that may or may not be compressed, or a punched or expanded sheet metal pipe.

In another embodiment, the mixture of gas bubbles and liquid is brought at the upper end of the rising tube into an auxiliary flame area coming for example from a conventional gas burner.

The method and device may also be used to obtain a coloured flame lamp.

The method and device are then defined as shown above except for the fact that:

a) the liquid contains at least one compound capable of colouring a flame; these are generally compounds of a number of metals and,

b) the mixture of liquid and combustible gas obtained at the top of the rising tube is ignited and allowed to burn, possibly in contact with the flame of an auxiliary burner.

The combustible gas is for example methane, ethane, propane, butane, isobutane or dimethyl-oxide, and the liquid is preferably combustible. This liquid may even be aqueous if its proportion is low relative to that of the combustible gas; it then acts only as a solvent for the compounds intended to colour the flame.

For reasons of safety, a liquid may be used that has a high flash point, for example above 50° C. and preferably above 80° C.

In order to colour the flame, a compound is used that is in fine suspension or preferably dissolved in the liquid, with one of the constituent elements being selected for the flame coloration it produces. These compounds are well known to the man skilled in the art.

As examples may be cited:

lithium: red,

sodium: yellow,

copper in halogenated compositions: green or blue,

borates: Red,

carbon: yellow or white

These transmitter compounds may be mineral, for example nitrate or chloride, particularly if the liquid is aqueous or aqueous-alcoholic or aqueous glycolic, or organic, for example acetate, hexanoate, ethylhexanoate, stearate, oleate, acetylacetonate, if the liquid is organic (hydrocarbons, alcohol, glycol, amide, for example). Liquids are preferred which combust without significant sooting.

As may be noted, one advantage of the invention is that the device described does not require any moving mechanical parts. Another advantage lies in the fact that the rate of flow of the liquid produced by the string of bubbles depends little on the level of liquid in the load tank; the difference in level between the liquid in the tank and the top of the rising tube is, preferably, between 5 and 50 centimetres, although much greater differences in levels are conceivable.

The unit quantity of liquid (in other words the quantity of liquid leaving the rising tube, between each gas bubble) brought to the top of the rising tube may be adjusted according to the invention by adjusting the size of the bubbles in relation to the cross-section of the rising tube.

The quantity of combustible gas required to provide a steady rate of flow is generally about 5 to 20 times the volume of feed liquid, but may be easily determined, even outside these values, by the man skilled in the art.

The feed may be started and stopped by opening and closing the gas inlet.

The method described by the invention allows easy control of several liquid feed device units simply by opening a gas valve controlling the gas feed to several rising tubes, possibly fed by different liquids and possibly different rates of flow.

In another embodiment, the liquid is scented and its combustion spreads an odour of scent into the surrounding atmosphere. This is the case with a scented oil, for example pine essence.

The appended drawings show various embodiments of the invention.

FIG. 1 describes the basic principle of the invention according to the first embodiment of the invention,

FIG. 2 shows in partial view an embodiment of the bubble chamber,

FIG. 3 shows a preferred embodiment of the invention according to the first embodiment of the invention.

FIGS. 4 and 5 show the second embodiment of the invention.

FIG. 6 shows the third embodiment of the invention.

It must be understood that these illustrations in no way limit the scope of the invention and that this is only limited by the scope of the following claims.

The device in FIG. 1 comprises a tank of liquid 1, communicating at its base, via a pipe 2, with a bubble chamber 3, which is topped by a rising tube of small diameter 4 provided with a combustible gas inlet 5 in the form for example of a nozzle, the level of which in said chamber is above the level of the outlet port 6 of the pipe 2, so as to avoid a discharge of gas back towards the tank of liquid. The gas comes, via the pipe 7, controlled by the tap 8, from the gas tank 9. At the top of the rising tube 4 is placed a burner 10, for example in the form of a grid or of a porous fire resistant material. The level of liquid 11 in the tank is kept above the level of the lower end 15 of the rising tube and below the level of the upper end 16 of said rising tube.

The upper part of the bubble chamber is in the form of a downward-widening funnel.

The cross-section of the rising tube is sufficiently small and the cross-section of the gas inlet sufficiently large for the gas to rise in said tube in the form of individual successive bubbles such as 13 and 17 each occupying the quasi-totality of the internal transverse cross-section of the tube, each bubble being separated from the next one by a portion of entrained liquid, such as 14 and 18. The rate of flow of the gas is controlled in such a way that the gas rises in the bubble chamber in the direction of the rising tube in the form of individual successive bubbles and not in the form of a continuous jet. The rate of flow of the gas must also be sufficiently small so as not to exceed the rate of flow of the gas in the rising tube; should the reverse be true, the gas would accumulate beneath the rising tube and no longer fulfil its function as a liquid portion-entraining admixture.

In FIG. 1, the gas is obtained by vaporising a pressurised liquid 12 such as butane.

To avoid a gas leak from the chamber 3 to the tank 1, the liquid outlet port 6 in the bubble chamber may comprise a non-return valve or have a minimal cross-section. This may for example be a micro-port, a narrow slot or a porous partition.

In operation, the combustible gas, for example butane, is ignited at the top of the rising tube. Depending on the nature of the compounds which have been dissolved in the liquid, flames (F) of different colours may be obtained.

FIG. 2 shows a particular embodiment of the bubble chamber 3 here consisting of the lower part of the rising tube 4. In this embodiment, the rising tube 4 may be raised or lowered inside a fixed external tubular enclosure 19. The connection not shown here between the tube 4 and the enclosure 19 may be a simple friction coupling (for example an O-ring) or better comprise a screw thread such as 23 (see FIG. 3); in the latter case, rotating the tube 4 makes it possible to raise it or to lower it with more accuracy than with simple friction. In the lowered position, the tube 4 is supported against a coupling 20, for example made of elastomer, and the liquid in the tank 1 placed in the upper part of the enclosure 19 cannot penetrate into the bubble chamber 3. Raising the tube 4 entails raising the coupling 20 and a hollow part 21 which on the one hand supports the coupling 20 and on the other hand acts as a needle valve 25 to shut off or open the flow of gas from the tube 7. This rise is caused by relaxing the compressed spring 22, placed at the lower part of the enclosure 19. The combustible gas is then able to rise in the hollow part then in the injector 5, in the chamber 3 and in the tube 4. When the spring is completely relaxed, the coupling 20 no longer rises and continuing to raise the tube 4 allows the liquid in tank 1 to penetrate into the bubble chamber 3 passing between the base 24 of the bubble chamber and the coupling 20. The gas then forms a column of bubbles (not shown) in the bubble chamber and these bubbles as they then rise into the tube 4 entrain portions of liquid into this tube.

It will be noted that the enclosure 19 acts as a tank of liquid in its upper part (above the coupling 20) whereas in its lower part (below the coupling 20) it allows the gas coming from the tube 7 to pass.

FIG. 3 shows a complete installation operating as a flame lamp and using as a combustible gas source a tank of liquefied gas such as butane. The tank of liquefied gas 9 and the tank of liquid 1 containing a flame colorant are placed one below the other surrounding the rising tube and the gas inlet, in such a way as to make an autonomous assembly in a single piece. The operation is the same as in FIG. 2 or FIG. 1 and the numerical references in FIG. 3 have the same significance as in FIGS. 1 and 2. The references 23 and 27 to 29, which do not feature in FIGS. 1 and 2, have significance as follows: the reference number 23 represents the screw thread, or equivalent component, which allows the tube 4 to be raised or lowered. Reference number 27 denotes a liquid recovery cushion such as a metal sponge, a porous material or the like. Reference number 28 represents the filling ports of the tank of liquid 1. Reference number 29 represents a depression membrane or the equivalent.

The operation will be easily understood in the light of the description of FIGS. 1 and 2 and it will be sufficient therefore to give a brief summary of this operation. When the tube 4 is raised by rotating it around the screw thread 23, the spring 22 relaxes, the part 21 and the needle valve 25 are raised and the combustible gas (for example butane vapour) is able to penetrate into the chamber surrounding the spring; from there the gas passes through the port 21 a and rises in the tube 26 and the tube 4. When the spring is fully relaxed, the rise of the tube 4 allows the liquid in the tank 1 to penetrate into the bubble chamber 3 passing through the port 24 and to rise in it as far as the tube 4. As the tank 1 is not pressurised, the liquid is not able to rise by itself as far as the top 16 of the tube 4. On the other hand the gas forms individual bubbles 13, 17 in the tube 4 and these bubbles allow portions of liquid 14, 18 to rise as far as the top of the tube 4. It is then possible to ignite the gas mixed with the liquid at the top of the tube 4 either directly at the outlet of this tube or after passing through the porous cushion 27. In this way we have a flame (F) that is able to be coloured as a function of the compounds which have been dissolved or dispersed in the liquid in the tank 1.

FIGS. 4 and 5 illustrate the second embodiment of the invention.

In these figures, the rising tube 18 is surrounded by a controlled pressurised space, for example a closed space 31, which extends the bubble chamber 3 upwards and in which the liquid is able to rise or descend according to the pressure of the gas present in the upper part of said closed space. The gas arrives through the pipe 7 and the space 31 which extends the inlet pipe of the gas coming from a tank (not shown) such as the tank 9 in FIG. 1, and the liquid through the pipe 2, coming from a tank (not shown) such as the tank 1 in FIG. 1.

At rest, without injection of gas, the level of liquid in the space 31 is controlled by the level of the tank. It is above the level 32 of the base 15 of the rising tube 18. This level is shown in the diagram as 11 a (FIG. 4) or 11 b or 11 c (FIG. 5). When gas is injected through the pipe 7, this gas begins by collecting in the closed space 31 and, as its pressure increases, it pushes the liquid in the space 31 downwards as far as the level 32 of the bottom of the tube 18. If gas continues to be injected, a part of the liquid goes down again slightly below the level 32 and gas is able to escape through the tube 18, which causes a slight rise in the liquid a fraction of which will be sucked into the tube. The method is repeated, causing bubbles of gas separated by portions of liquid to rise in the tube. The space 31 is not however essential and the level 32 may be that of the top of the bubble chamber, the gas then being injected at this level or below.

The operation is substantially identical, whatever the gas injection point, in the liquid or above the liquid, and, in the first case (FIG. 4), the gas inflow may be exactly in the axis of the rising tube or offset relative to this axis. In the second case (FIG. 5), in operation, the inflow of gas into the liquid, and therefore into the bubble chamber, occurs at the level 32, approximately at the level of the bottom of the rising tube.

FIG. 6 shows a third embodiment of the invention.

In this figure, the gas inlet tube 7 is extended inside the rising tube 18 while still providing a space 33 allowing access by the liquid, which, in operation, reaches a level 11 a above the level of the bottom of the rising tube 18. If the internal cross-section of the gas inlet tube, at its upper end, is sufficient and is for example 25 to 85% of the internal cross-section of the rising tube (the internal cross-section of the tube of gas 7 being smaller than the internal cross-section of the rising tube), the bubbles formed, such as 17 and 13, given their tendency to increase their cross-section as they leave the tube 7, will occupy all the internal cross-section of the rising tube 18, which will allow the rise of a string of bubbles separated by portions of liquid such as 14 and 14′.

The following example, non-restrictive on the invention, is intended to illustrate this.

EXAMPLE

A coloured flame lamp consists of the following components: a tank of liquid 1 with a capacity of 250 millilitres is filled with a liquid consisting of 94% (by weight) of dimethylformamide, 4% of lithium nitrate and 12% of ammonium nitrate, the salts indicated being dissolved in the liquid. This tank is 6 cm high and it is fitted with an air inlet at the top with a bleed-proof device, and an outlet bringing liquid through a small pipe 2 to the bubble chamber 3. This bubble chamber, placed at the lowest part of the lamp, has a capacity of 2 millilitres; it is penetrated at the bottom by a gas inlet tube terminated by a port 5 with a diameter of 1.5 mm forming bubbles about 2 mm in diameter. At the top of the bubble chamber, vertically above the gas outlet port, is located the lower end of a stainless steel tube 4 with an external diameter of 2 mm and an internal diameter of 1.6 mm. This tube 4 is placed vertically and is 18 cm long.

The tubing bringing the gas into the bubble chamber is fed by a tank of liquefied butane 9 with a capacity of 25 grams fitted with a control valve 8 equipped with an upstream throttling ensuring a rate of flow of 5 grams per hour of gas when operational.

At the top of the vertical tube and outside it is placed a metal wick 27 intended to retain the liquid emerging from this tube during combustion.

When the gas aperture is activated, the butane gas emerges at the top of the tube 4 with a small rate of flow as indicated above and allows a small flame the size of that of a cigarette lighter to be lit. After a few seconds, the liquid rises in small portions 14, 18 separated by a string of gas bubbles 13, 17 provided by the device of the invention according to a rate of flow of about 50 grams per hour. It is easily ignited in contact with the small butane flame and produces a beautiful stable red flame (F) about 5 to 6 centimetres high, with no risk of bleeding. The lamp thus obtained has an autonomous life of about 5 hours.

Given the small rate of flow of the gas causing the liquid to rise, it is advisable not to lose any of the latter's efficiency, which could occur if this gas were to dissolve in the feed liquid. In the event of the gas selected having substantial solubility in the selected liquid, the drawback cited would be avoided by dissolving in the liquid constituents that reduce the solubility of the gas. In example 2, the addition of ammonium nitrate allows significant dissolution of butane in the dimethylformamide to be avoided. Furthermore, this addition encourages the decomposition of the deposit containing the colouring metals (such as lithium) via micro-explosions in the flame. 

1. A method for producing a flame by combustion of a combustible gas at the upper end of a rising tube of small internal transverse cross-section, characterised in that: a) a supply of a liquid is set up with its level being maintained both below that of the upper end of said rising tube and above that of the lower end of this same tube, b) the supply of liquid is brought into contact with a chamber, called a bubble chamber, that also communicates with the lower end of said rising tube, or is inserted into the latter in its lower part and also communicating with a combustible gas source by means of a gas inlet port, c) while maintaining the liquid level in the supply as shown above, the combustible gas is allowed to pass into the bubble chamber through the gas inlet port at a sufficient rate of flow to produce at the base of the rising tube a sequence of combustible gas bubbles in the liquid, said rate of flow being however smaller than that which would lead to an accumulation of gas below the rising tube such that the liquid would no longer have access to the lower end of this tube, and said sequence of combustible gas bubbles separated by portions of entrained liquid is allowed to rise in the rising tube, and d) the mixture of combustible gas bubbles and liquid is ignited and allowed to burn, at said upper end of the rising tube, so as to operate as a flame lamp.
 2. Method according to claim 1, characterised in that: a) a supply of a liquid is set up with its level being maintained both below that of the upper end of said rising tube and above that of the lower end of this same tube, b) the supply of liquid is brought into contact with a chamber, called a bubble chamber, that also communicates on the one hand, at its upper part, with the lower end of said rising tube and on the other hand with a combustible gas source by means of a gas inlet port which is located at a level of the bubble chamber below the level of the lower end of the rising tube, the cross-section of the gas inlet port in the bubble chamber being sufficient so as to produce in the bubble chamber liquid successive gas bubbles with a cross-section at least equal to the internal transverse cross-section of the rising tube, the liquid in the supply being brought into contact with the bubble chamber away from the path of said gas bubbles, c) while maintaining the liquid level in the supply as shown above, the combustible gas is allowed to pass into the bubble chamber through the gas inlet port at a sufficient rate of flow to produce a sequence of combustible gas bubbles in the liquid, said rate of flow being smaller however than that which would lead to an accumulation of gas bubbles at the top of the bubble chamber, so as to allow said sequence of combustible gas bubbles separated by portions of entrained liquid to rise in the rising tube and to release said portions of liquid at the upper end of said rising tube, and d) the mixture of combustible gas bubbles and liquid is ignited and allowed to burn, at said upper end of the rising tube, so as to operate as a flame lamp.
 3. Method according to claim 1, wherein the level of the lower end of the rising tube is lower than the top of the bubble chamber and wherein the combustible gas is allowed to pass under sufficient pressure so as to push back the liquid, present outside the rising tube, from its rest level, downwards, as far as the level of the lower end of the rising tube, thus allowing the gas in the form of successive bubbles, and the liquid to gain access by turns to this lower end of the rising tube.
 4. Method according to claim 1, wherein the gas is allowed to pass directly inside the rising tube, at its lower part, which acts as the bubble chamber.
 5. Method according to claim 1, characterised in that it is implemented in a rising tube of internal cross-section of less than 1 square centimetre and preferably less than 10 square millimetres.
 6. Method according to claim 1, characterised in that it is implemented with a bubble chamber with a transverse cross-section larger than both the maximum internal transverse cross-section of the rising tube and the transverse cross-section of the gas inlet port in the bubble chamber.
 7. Method according to claim 2, characterised in that it is implemented with a gas bubble outlet port whose cross-section represents 75 to 200% of the maximum internal cross-section of the rising tube.
 8. Method according to claim 1, characterised in that the rate of flow of gas is 5 to 20 times the rate of flow of liquid on a volumetric basis.
 9. Method according to claim 1, characterised in that ignition occurs on the surface of a piece of metal gauze, a compressed wire yarn sleeve or a porous body that is non-combustible or difficult to combust placed at the upper end of the rising tube.
 10. Method according to claim 1, characterised in that the liquid contains in solution or in suspension at least one chemical compound selected for the flame coloration it produces, so as to operate as a coloured flame lamp.
 11. Method according to claim 1, characterised in that the mixture of gas bubbles and liquid is burnt at the upper end of the rising tube in contact or mixed with an auxiliary flame.
 12. Device including a rising tube (4) communicating via its lower end with a chamber called a bubble chamber (3), said bubble chamber being furthermore in communication on the one hand with a tank (1) for liquid and on the other hand with a combustible gas source (9), said tank being able to contain said liquid at a level both above the level of the lower end of the rising tube and below the level of the upper end of said rising tube, the bubble chamber and the combustible gas source communicating by means of a gas inlet port (5), said device being characterised in that it additionally comprises a burner (10) at the upper end of the rising tube (4), intended for the combustion of the combustible gas and any liquid, as well as means for controlling the rate of flow of the combustible gas allowing the latter to pass into the liquid in the form of a string of successive gas bubbles with a cross-section at least equal to the internal cross-section of the rising tube, directed towards the base of the rising tube or introduced directly into it.
 13. Device according to according to claim 12, including a rising tube (4) communicating via its lower end with the upper end of a chamber called a bubble chamber (3), said bubble chamber being furthermore in communication on the one hand with a tank (1) for liquid and on the other hand with a combustible gas source (9), said tank being able to contain said liquid at a level both above the level of the lower end of the rising tube and below the level of the upper end of said rising tube, the bubble chamber and the combustible gas source communicating by means of a gas inlet port (5) located at a level of the bubble chamber below the level of communication of said chamber with the lower end of the rising tube and the bubble chamber and the tank of liquid communicating by means of at least one liquid inlet port (6) located away from the rising path followed by the bubbles of combustible gas which are able to form when the bubble chamber is filled with liquid and when the gas is allowed to pass into said chamber, said device being characterised in that it additionally comprises a burner (10) at the upper end of the rising tube (4), intended for the combustion of the combustible gas and any liquid, as well as means for controlling the rate of flow of the combustible gas allowing the latter to pass into the bubble chamber in the form of a string of successive gas bubbles with a cross-section at least equal to the internal cross-section of the rising tube.
 14. Device according to claim 12, wherein the upper part of the bubble chamber (3) is in the form of a downward-widening funnel, intended to receive the gas bubbles and to direct them towards the lower end of the rising tube (4), the transverse cross-section of the bubble chamber being greater than both the maximum internal transverse cross-section section of the rising tube and the transverse cross-section of the gas inlet port (5) in the bubble chamber.
 15. Device according to claim 12, wherein the bubble chamber (3) is located at least partly inside the tank of liquid (1).
 16. Device according to claim 12, wherein the tank of liquid comprises a well at its base, and wherein the bubble chamber is placed at least partly in said well.
 17. Device according to claim 12, wherein the rising tube (4) has at all points an internal cross-section of less than 1 square centimetre and preferably less than 10 square millimetres.
 18. Device according to claim 13, wherein the cross-section of the gas bubble outlet port represents 75 to 200% of the maximum internal cross-section of the rising tube.
 19. Device according to claim 12, wherein the burner consists of a piece of metal gauze, a compressed wire yarn sleeve or a porous body that is non-combustible or difficult to combust.
 20. Device according to claim 12, additionally comprising an auxiliary gas burner placed in contact with the burner at the upper end of the rising tube.
 21. Use of the method according to claim 12, in order to produce a coloured flame, the liquid containing in solution or in suspension at least one chemical compound selected for the flame coloration it produces when the combustible gas and possibly said liquid is ignited in the burner (10). 